1. Field of the Invention
This invention relates to an angle-bar device used for changing the direction of running of paper webs in a rotary printing press which is put to use by allowing the paper webs to run continuously along their respective paths.
2. Description of the Prior Art
In an angle-bar device for use in a rotary printing press using paper webs, during the operation of the rotary printing press, portions of each of the angle-bars just in front and just in rear of a paper web guiding zone around which a running paper web W is guided in contact therewith are deposited with ink and paper dust from the paper web thereby forming deposits "a", "b". These deposits give not a little bad influence on the paper web running around the angle-bars, which includes, for example, spoiling the portions of the paper web which are brought into contact with the angle-bars, and application of irregular tension on the running paper web, etc.
Thereupon, to prevent the angle-bars from being deposited with ink and paper dust, etc., the following measures are disclosed. For example, in the article entitled "Turning Bar" from lines 23rd to 33rd, on the right column, page 237 of "Revised and Enlarged Printing Dictionary" (First edition issued by choyo society, Printing Bureau on 30th June Showa 62nd), there are described a method of rotating the turning bars or the angle-bars little by little to prevent the turning bars from being desposited with ink and paper dust, etc.,and another method for blowing off air to maintain a clearance between each of the angle bars and the paper web. Further, described in the publication of Japanese Laid-open Utility Model Application No. HEI 2-46627 is an apparatus for ejecting air from openings formed in the peripheral surfaces of turning bars or angle-bars to space a paper web from the peripheral surfaces to thereby create a clearance between each of the angle-bars and the paper web guided therealong.
The above-mentioned method for rotating the angle-bars little by little is aiming at rotating the angle-bars to constantly change the paper web guiding zones and the portions just in front and just in rear of the guiding zones, thereby preventing these portions from being deposited with ink and paper dust, etc. However, in rotary printing presses of today for printing newspaper wherein paper webs are run at about 10 meters per second, since deposition of ink and paper dust, etc., occurs very quickly, it is necessary to rotate the angle-bars at a comparatively fast speed to prevent the occurrence of such a phenomenon. In case the angle-bars are rotated so quickly, the tension on the paper web becomes unbalanced, thus creasing or tearing it. Further, considering the paper web which is guided around the upstream and downstream angle-bars, the paper web guided around the upstream angle bar will reach a position between the upstream and downstream angle bars while it is being pulled by an upstream drag roller, whilst the paper web which has been guided around the downstream angle-bar is pulled by a downstream drag roller against the frictional force caused by the downstream angle-bar, and then drawn out. Consequently, the portion of the paper web which is guided around the peripheral surface of the downstream angle-bar and is run out therefrom is subjected to a comparatively high tension and kept in a satisfactory sliding contact with the downstream angle-bar, while the portion of the paper web which is guided around the peripheral surface of the upstream angle-bar and is run forwards therefrom is subjected to a low tension so that its sliding contact with the upstream angle-bar becomes imperfect. Therefore, even if attempt is made to wipe off ink and paper dust, etc., once deposited on the upstream and downstream bars with the paper web which is running around them while both the angle-bars are rotated little by little, such ink and paper dust, etc., cannot be completely wiped off by means of the upstream angle-bar.
On the other hand, in the above-mentioned method and device for spacing the paper web slightly away from each of the angle-bars by spouting air between them, it is required to provide either a long conduit connecting each of the angle-bars and a pressurized air supply source or an air current generator (for example, an electric-motor driven fan) directly connected to each of the angle-bars, and in spite of the need for supply of a considerably large amount of air to be spouted, the paper web cannot be held continuously in spaced apart relationship from the peripheral surfaces of the angle-bars so as to follow some change in tension on the running paper web. Consequently, in spite of the large scale of the device, the primary object of spacing the paper web away from the angle-bars cannot be achieved satisfactorily, and when the device is used for a long period of time, not only the portions of the angle-bars just in front and just in rear of the paper web guiding zones, but also the pressurized air spout holes are deposited with ink and/or paper dust, etc., so that desired result cannot always be obtained. Further, the sound generated by blowing-off of pressurized air offends the ear appreciably.
Therefore, in high speed operation rotary printing presses which have been developed of late years, ink and paper dust, etc., deposited on the angle-bars have been wiped off manually by the operators after printing operation.
However, such a wiping-off operation is time-consuming and inefficient work, and also because of the configuration of the rotary printing press the angle-bars are installed in most cases at an elevated spot where other members (for example, guide rollers) are located intricately, so that the operators are forced to assume a cramped and unstable posture with much physical and mental burden.
For this reason, it has been desired strongly from the aspects of safe operation and reduction of labor to provide an angle bar device whose peripheral surface can be kept clean without causing any trouble such as tear of paper web, etc even for high speed operation rotary printing presses.